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[PIN+]: prions beget prions
A selection of talks on Biochemistry
The ERK1/2 MAPK cascade
- Prof. Melanie H. Cobb
- University of Texas Southwestern Medical Center at Dallas, USA
Amino acid conjugation: mechanism and enzymology
- Dr. Kathleen Knights
- Flinders University, Australia
In this seminar, I will tell you how the presence of one yeast prion can enhance the appearance of other yeast prions.
According to the prion paradigm in yeast cells can propagate prion proteins in either the normal form or the prion form. When propagated in the prion form, they have a different phenotype than in cultures where the protein is propagated and the normal form. Cells with the prion in the normal form can be converted into prion cultures by being infected with prion seed. Evidence suggests that the prion seed is a fiber and that the normal molecules join this fiber at the ends.
The growth of the prion fiber is limited by the fact that it only has two ends. And as you could imagine, its ability to segregate into budding daughter cells is also limited by the number of prion seeds that are present in the mother. The Hsp104 chaperone whose activity is known to disaggregate aggregated proteins provides the important activity for the prion of cutting these fibers into pieces, which provides additional ends and additional seeds that can then segregate into the daughters. In the absence of Hsp104 of course, the prions are not cut and they fail to segregate and are lost, leading to the curing of cells of the prion. This also explains how the low levels of guanidine hydrochloride, known for many years to cure cells of prions works and it does so we now know by inhibiting the activity of the Hsp104 chaperone.